The present invention concerns a method for producing hydrocarbon gas from subterranean aquifers and, particularly, for producing hydrocarbon gas initially in water solution in the aquifers.
Waters in a large number of aquifers throughout the world contain very large quantities of gas in water solution. Aquifer waters underlying the Texas-Louisiana coastline were estimated to potentially contain about 50 thousand trillion cubic feet of gas. (See "Natural Gas Resources of Geopressured Zones in the Northern Gulf of Mexico Basin" by P. H. Jones presented at the "Forum on Potential Resources of Natural Gas" at Louisiana State University, Baton Rouge, La., on Jan. 15, 1976).
The effect of pressure, temperature and water salinity on solubility of natural gas in water is well known (as, for example, described in an article entitled "pressure-Volume-Temperature and Solubility Relations for Natural Gas-Water Mixtures" by C. R. Dodson and M. B. Standing, Drilling and Production Practice, API, 1944). Of the parameters which affect the amount of gas which can be in water solution pressure is the most important. At depths of about 15,000 feet, "geopressured" aquifers along the Texas-Louisiana Gulf Coast typically have pressure on the order of 13,000 psig and the water contains on the order of 30 standard cubic feet (scf) or more of solution gas per barrel (B).
Aquifer waters can also contain less gas in solution than that corresponding to saturation, in which case they are "undersaturated". It is well known that water resident in certain geological formations in certain geographic areas almost always contains gas in solution closely corresponding to "saturated" conditions.
Aquifer waters with hydrocarbon gas in solution at saturation levels, or near saturation levels, are most suitable for application of the present invention.